As the factors participating in adhesion to the extracellular substrate of animal cells, there have been known fibronectin, vitronectin, osteopontin, collagen, thrombospondin, fibrinogen, von willebrand factor, etc. These proteins include tripeptide sequence of -Arg-Gly-Asp- as cell recognition site. This tripeptide is recognized by at least one protein belonging to the receptors integrins, which are heterodimeric proteins consisting of sub-units combined to two membranes [Science, 238, 491 (1987)].
Structurally related integrin receptors, which recognize the amino acid sequence -Arg-Gly-Asp-, are known to express at the extracellular surface glycoprotein of platelets, endothelial cells, leucocyte, lymphocyte, monocyte and granulocyte. Compounds having the amino acid sequence -Arg-Gly-Asp- are competitively bound to the site to be bound with intracellular adhesive factors to thereby inhibit the binding of intracellular adhesive factors. As such substances for inhibiting intracellular adhesion, there has been known, for example, H-Gly-Arg-Gly-Asp-Ser-Pro-OH.
When blood vessels are injured, platelets are activated with, for example, endothelial collagens, which causes binding of fibrinogen to platelets, i.e. platelet aggregation, to form thrombus. The interaction between platelets and fibrinogen takes place through GP IIb/IIIa, this being an important characteristic feature of platelet aggregation. Cell adhesion-inhibiting substances can inhibit platelet aggregation due to substances causing platelet aggregation such as thrombin, epinephrine, ADP and collagen.
Besides, cell-adhesion inhibiting substances are expected to be useful as drugs for suppression of metastasis of tumor cells (inhibition of fixed adhesion at the site where the tumor cells are migrated).
Linear or cyclic peptides containing the amino acid sequence, -Arg-Gly-Asp- (RGD) have been known as cell-adhesion inhibiting substances [Journal of Biological Chemistry (J. Biol. Chem.), 262, 17294 (1987) and Japanese published unexamined patent application No. 174797/1990, among others].
And, non-peptide compounds having an anti-thrombotic action are disclosed in Japanese published unexamined patent application No. 264068/1992 and EPA 505868. Further, compounds having pyridyl-piperazine or pyridazinyl-piperazine, which have an anti-thrombotic action, are disclosed in WO 96-24581. And, such drugs as aspirin, heparin and ticlopidine are known to show undesirable side effects such as prolongation of bleeding time. As known platelet aggregation inhibiting substances which are slight in the action of prolonging bleeding time, cyclic peptide derivatives are described in the Japanese publication of translations of International patent application No. 509551/1994.